Sometimes Mister B has free evenings when he doesn't know what to do. Fortunately, Mister B found a new game, where the player can play against aliens. All characters in this game are lowercase English letters. There are two players: Mister B and his competitor. Initially the players have a string s consisting of the first a English letters in alphabetical order (for example, if a = 5 , then s equals to " abcde "). The players take turns appending letters to string s . Mister B moves first. Mister B must append exactly b letters on each his move. He can arbitrary choose these letters. His opponent adds exactly a letters on each move. Mister B quickly understood that his opponent was just a computer that used a simple algorithm. The computer on each turn considers the suffix of string s of length a and generates a string t of length a such that all letters in the string t are distinct and don't appear in the considered suffix. From multiple variants of t lexicographically minimal is chosen (if a = 4 and the suffix is " bfdd ", the computer chooses string t equal to " aceg "). After that the chosen string t is appended to the end of s . Mister B soon found the game boring and came up with the following question: what can be the minimum possible number of different letters in string s on the segment between positions l and r , inclusive. Letters of string s are numerated starting from 1 . First and only line contains four space-separated integers: a , b , l and r ( 1 ≤ a , b ≤ 12 , 1 ≤ l ≤ r ≤ 10 9 ) — the numbers of letters each player appends and the bounds of the segment. Print one integer — the minimum possible number of different letters in the segment from position l to position r , inclusive, in string s . In the first sample test one of optimal strategies generate string s = " abababab... ", that's why answer is 2 . In the second sample test string s = " abcdbcaefg... " can be obtained, chosen segment will look like " bcdbc ", that's why answer is 3 .